Lévai Olga, Feistel Torben, Breer Heinz, Strotmann Joerg
University of Hohenheim, Institute of Physiology, 70593 Stuttgart, Germany.
J Comp Neurol. 2006 Oct 1;498(4):476-90. doi: 10.1002/cne.21067.
Recent evidence indicates that the vomeronasal organ (VNO) of mice not only responds to pheromones but also to odorants. To analyze whether genes encoding odorant receptors (ORs) are expressed in the VNO, reverse transcriptase-polymerase chain reaction analyses were performed. These led to the identification of 44 different OR genes, comprising class-I and class-II receptors. The genes encoding these receptors were scattered over several gene clusters. The respective OR genes were concomitantly expressed in cells of the main olfactory epithelium (MOE). Although the cells in the MOE were zonally distributed, no such patterns were displayed in the VNO. Cells expressing ORs in the VNO were positive for the TRP2-channel and Galphai, a marker for vomeronasal neurons of the apical layer. In transgenic mice, which coexpress histological markers with the receptor mOR18-2, characteristic morphological differences between cells expressing this receptor in the VNO compared with the MOE became evident. Visualizing the axonal processes of VNO cells expressing distinct ORs revealed that they project to the accessory olfactory bulb (AOB). Axon fibers were visible exclusively in the anterior subdomain; here, they converged into glomerular-like structures positioned at the very rostral tip of the AOB. The findings that a set of ORs is expressed in cells located in the apical layer of the VNO with typical features of VNO sensory neurons that project their axons to the anterior part of the AOB suggest that this population of sensory cells may be considered as a unique facet of the complex chemosensory system.
最近的证据表明，小鼠的犁鼻器（VNO）不仅对信息素起反应，而且对气味剂也有反应。为了分析编码气味受体（OR）的基因是否在VNO中表达，进行了逆转录聚合酶链反应分析。这些分析鉴定出44种不同的OR基因，包括I类和II类受体。编码这些受体的基因分散在几个基因簇中。各自的OR基因在主嗅上皮（MOE）的细胞中同时表达。尽管MOE中的细胞呈带状分布，但VNO中未显示出这种模式。VNO中表达OR的细胞对TRP2通道和Galphai呈阳性，Galphai是顶层层犁鼻神经元的标志物。在与受体mOR18-2共表达组织学标志物的转基因小鼠中，与MOE相比，VNO中表达该受体的细胞之间的特征性形态差异变得明显。可视化表达不同OR的VNO细胞的轴突过程显示，它们投射到副嗅球（AOB）。轴突纤维仅在前亚域可见；在这里，它们汇聚成位于AOB最前端的肾小球样结构。一组OR在位于VNO顶层层的细胞中表达，这些细胞具有VNO感觉神经元的典型特征，其轴突投射到AOB前部，这一发现表明，这群感觉细胞可能被视为复杂化学感觉系统的一个独特方面。
